The following discussion of the background art is intended to facilitate an understanding of the present invention only. The discussion is not an acknowledgement or admission that any of the material referred to is or was part of the common general knowledge as at the priority date of the application.
A turbocharger, or ‘turbo’ as typically known colloquially, is a turbine-driven forced induction device that increases an internal combustion engine's efficiency and power output by forcing extra air into the combustion chamber. This improvement over a naturally aspirated engine's output is due to the occurrence that the turbo can force more air, and proportionately more fuel, into the combustion chamber than atmospheric pressure alone.
A supercharger is another type of forced induction device. A key difference between a turbocharger and a conventional supercharger is that a supercharger is mechanically driven by the engine, often through a belt connected to the crankshaft, whereas a turbocharger is powered by a turbine driven by the engine's exhaust gas. Generally, a turbocharger consists of a turbine operatively driven via exhaust gas, a compressor for compressing atmospheric air fed into a combustion chamber of an engine, and a centre housing for housing the linked turbine and compressor as some manner of rotating assembly.
Compared to a mechanically driven supercharger, turbochargers tend to be more efficient, but less responsive. However, in contrast to supercharging, the primary disadvantage of turbocharging is generally what is referred to as “turbo lag” or “spool time”. This is the time between the demand for an increase in power (the throttle being opened) and the turbocharger providing increased intake pressure, and hence increased power.
Throttle lag occurs because turbochargers rely on the buildup of exhaust gas pressure to drive the turbine. In variable output exhaust systems, such as automobile engines, exhaust gas pressure at idle, low engine speeds, or low throttle is usually insufficient to drive the turbine. Inertia, friction, and compressor load are the primary contributors to turbocharger lag. Superchargers do not suffer this problem, because the turbine is eliminated due to the compressor being directly powered by the engine. With a turbocharger, only once the engine reaches sufficient speed does the turbine start to spool up, or spin fast enough to produce intake pressure above atmospheric pressure.
The boost threshold of a turbocharger system is the lower bound of the region within which the compressor operates. Below a certain rate of flow, a compressor produces insignificant boost. This limits boost at a particular compressor revolutions (RPM).
A number of solutions have been proposed to address the problems associated with turbo lag and boost threshold, including twin-charging setups (having both turbocharger and supercharger on a single engine), twin-turbo arrangements, twin-scroll turbochargers, variable-geometry turbochargers, and so-called e-boosting, which relies on electrical means to bring a turbocharger up to a required speed. Other proposed solutions include a variety of pneumatic, hydraulic and/or mechanical systems. However, all of the known prior art systems are generally complex, expensive and require considerable engineering expertise to realise and operate.
The present invention seeks to propose possible solutions, at least in part, in amelioration of the known shortcomings in the art.